For centuries, the ocean provided a linchpin for New England’s economy, from fishing grounds that brought the first Europeans, to whaling that made New Bedford the nation’s richest city, to merchant ships that built New England’s first great fortunes.

Now the region is reinventing its maritime industry again, turning to the sea not for fish or whales or trade, but energy. From the Bay of Fundy to Long Island Sound, new technologies are harnessing the power of ocean tides and winds, promising not only an inexhaustible source of energy, but also hundreds of jobs, billions in revenues, and new life for struggling fishing communities along New England’s 473-mile coastline.

This future is still far off, but the first steps toward it are underway. Since September, an underwater generator built by a Maine company has used the powerful tides of Cobscook Bay near the Canadian border to make electricity distributed by local utilities. Researchers at Woods Hole Oceanographic Institution, as well as universities in Massachusetts, New Hampshire, and Rhode Island, are working together to demonstrate similar technologies in the Cape Cod Canal and ­Muskeget Channel off Martha’s Vineyard.

The developers of Cape Wind have begun surveying the site in Nantucket Sound where they plan to erect 130 turbines to supply power for Massachusetts’ biggest utilities, NStar and National Grid. Fourteen miles south of Martha’s Vineyard, more turbines could be built in a 1,160-square-mile swath of federal waters that US officials have designated for offshore wind development.

Ocean energy is also generating economic activity on land. The nation’s first commercial testing facility for large wind turbine blades opened in Charlestown last year to support blade designers and manufacturers developing advanced materials that can stand up to harsh winds and elements offshore. The center helped persuade TPI Composites, an Arizona firm that makes blades for companies such as GE Energy, to open a development facility in Fall River.

Siemens AG, a German conglomerate, has also opened an office in Massachusetts dedicated to offshore wind power development, while others like Mass Tank Sales Corp., a Middleborough firm that makes water and fuel tanks, has a preliminary agreement to build foundations for Cape Wind’s turbines.

Quantifying just how big the ocean-based clean energy industry could be for New England is difficult, but analysts and others agree that it could be worth billions.

One study of the region’s marine science and technology industry by the University of Massachusetts’ Donahue Institute estimated the sector produced nearly $5 billion in sales for electronics equipment, surveying, research, and other activities in 2004. John Miller, director of the New England Marine Renewable Energy Center — a consortium of universities, research institutions, and industry, developing ocean energy technologies — estimated that waves, tides, and offshore winds could eventually meet New England’s entire demand for electricity.

“You’re talking gigawatts of power potential,” said Sue Reid, director of the nonprofit Conservation Law Foundation in Massachusetts, “so scale that up and the jobs scale up accordingly.” A gigawatt is 1 billion watts of power.

The East Coast is a prime candidate for ocean-energy development for several reasons. In addition to the obvious — access to offshore locations — the region has high energy costs, making wave, tidal, and offshore wind power more competitive with traditional producers. Another advantage: an existing maritime infrastructure of commercial piers and boat ramps, support vessels such as barges and tugs, and experienced, skilled seamen.

Officials in the region’s traditional port cities are promoting this infrastructure as they position their communities — many of them struggling — as locations that can support and service offshore energy. In New Bedford, where unemployment is near 12 percent, officials are waiting for a permit from the federal Environmental Protection Agency to expand the seaport to become a staging area for Cape Wind’s construction.

Rhode Island port officials hope to develop another staging area in North Kingstown.

In Gloucester, home of Gorton’s, the company that helped make fish sticks a meal-time staple, Mayor Carolyn Kirk said ocean energy could help revive a maritime industry that has been hard hit by federal fishing restrictions and other regulations aimed at rebuilding depleted fish stocks.

Kirk said the sea still remains Gloucester’s best resource. In recent years the city has held summits on revitalizing the harbor, creating a maritime development fund, and attracting funding for an ocean research lab.

“The ocean — let’s turn that into a positive,” Kirk said. “We have a harbor, we have access to research grounds. We have experienced captains, we have vessels, we have shoreside services.”

Despite progress, it will be several years yet before New England’s ocean energy industry is firmly established and competitive with traditional power-generating sources, ­according to the Electric Power Research Institute, a California nonprofit energy research organization. How fast the industry advances will depend on several factors, including environmental regulations, government support, and policies like those in Massachusetts that promote the development and use of alternative energy.

Another key factor is the cost of fossil fuels such as oil and natural gas. Rock bottom natural gas prices — the lowest in about a decade because of North American production boom — are slowing the development of alternative energy projects, including those offshore.

But ocean energy is still moving forward. Maine is already benefiting from roughly $14 million in investments made by Ocean Renewable Power Co., the Portland firm that developed the nation’s first commercial tidal energy project in Cobscook Bay, between Eastport and Lubec, the nation’s eastern most communities. The project, producing enough power for about 25 homes, will eventually become part of a network of 20 ocean generators making enough electricity to power 1,200 homes.

In a county where the unemployment rate is nearly 10 percent, Ocean Renewable Power’s work has helped employ local fisherman, harbor pilots, and others who helped with siting and supplying the project.

“It supports barges, cranes used in the marine environment, support vessels, tugs, [and] boat ramps and commercial piers,” said John Ferland, vice president of project development for Ocean Renewable Power Co. “It’s truly a way of taking what has existed traditionally and opening up a new market opportunity.”